Cryptographically Sound Theorem Proving

Christoph Sprenger, Michael Backes, David Basin, Birgit Pfitzmann, and Michael Waidner.
in Proceedings of 19th IEEE Computer Security Foundations Workshop (CSFW), pp. 153-166, July 2006.

Abstract

We describe a faithful embedding of the Dolev-Yao model of Backes, Pfitzmann, and Waidner (CCS 2003) in the theorem prover Isabelle/HOL. This model is cryptographically sound in the strong sense of blackbox reactive simulatability/ UC, which essentially entails the preservation of arbitrary security properties under active attacks and in arbitrary protocol environments. The main challenge in designing a practical formalization of this model is to cope with the complexity of providing such strong soundness guarantees. We reduce this complexity by abstracting the model into a sound, light-weight formalization that enables both concise property specifications and efficient application of our proof strategies and their supporting proof tools. This yields the first tool-supported framework for symbolically verifying security protocols that enjoys the strong cryptographic soundness guarantees provided by reactive simulatability/ UC. As a proof of concept, we have proved the security of the Needham-Schroeder-Lowe protocol using our framework.

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